A technique by which a transistor is formed using a semiconductor thin film formed over a substrate having an insulating surface has been attracting attention. Such a transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) and an image display device (also simply referred to as a display device). As a semiconductor film applicable to the transistor, a silicon-based semiconductor material is widely known; moreover, a metal oxide exhibiting semiconductor characteristics (an oxide semiconductor) has been attracting attention as another material.
For example, Patent Document 1 discloses a technique in which a transistor is manufactured using an amorphous oxide containing In, Zn, Ga, Sn, and the like as an oxide semiconductor.